The Research On The Application Of Quick-Setting Cement Paste For Earth-Rock Cofferdam Grouting

In the Hydropower construction projects or other underwater construction projects, cofferdam is widely used. In the river of rapid water speed, the use of earth-rock cofferdam is very common. High-pressure jet grouting is commonly used in the cofferdam seepage treatment. In such operating conditions, a relatively large leakage may occur after closed gas pumping. Grouting is a major problem in the anti-seepage grouting when larger head difference appears between the moving water in the upstream and downstream. Aiming at this problem, this paper, which is on the basis of the construction technology of the full investigation on such problems at home and abroad, obtains reasonable mixture ratio of quick-setting cement paste and applicable conditions for flow rate through physical performance tests of quick-setting cement paste and indoor impact simulation. The research result is transformed, and the improved construction equipment is applied to the upstream and downstream earth-rock cofferdams grouting construction of Qiaogong Hydropower Station.According to the laboratory test of quick-setting cement paste including two physical and mechanical performance tests and one indoor simulated impact test, we obtain five groups of mixture ratio of the quick-setting cement paste and five groups of physical and mechanical properties of paste. The results show that the slurry of the five groups has moderate ratios and it is easily mixed and pumped. Different ratios of the slurry can be selected under different conditions of use (porosity, water velocity, etc.). Indoor simulation of impact tests obtain four different flow rates, three different sets of slit width results which indicate that quick-setting cement paste is suitable for grouting and plugging construction conditions when the flow rate is less than1.5m/s.To meet the construction requirements, this research combines construction characteristics of the quick-setting cement paste, transforms mixing equipment and pumping equipment for cement paste grouting, and selects the appropriate pipe material.The research for quick-setting cement paste, which is applied to the upstream and downstream earth-rock cofferdams grouting construction of Qiaogong Hydropower Station, achieves good results. The geophysical means (borehole TV) are introduced in the construction process. It is local filled with graded aggregate combined with quick-setting cement paste grouting. The results show that, using quick-setting cement paste grouting and plugging technology is feasible and effective in the anti-seepage technique for an earth-rock cofferdam. The quick-setting cement paste is suitable for the formation plugging and the construction process is appropriate. As for the large leakage volume of flow rate more than1.5m/s and high velocity formation plugging, the earth-rockfill cofferdam is first filled with graded gravel or cotton yarn and other fiber materials. The quick-setting paste grouting is feasible and effective.